Late Miocene Cyclocarya (Juglandaceae) from Southwest China and Its Biogeographic Implications
Late Miocene Cyclocarya (Juglandaceae) from Southwest China and Its Biogeographic Implications
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DOI：
10.1086/692765
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发表时间：
2017-07
影响因子：
2.3
通讯作者：
Jing-Yu Wu;P. Wilf;S. Ding;P. An;J. Dai
中科院分区：
文献类型：
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作者：
Jing-Yu Wu;P. Wilf;S. Ding;P. An;J. Dai
研究的前提。青钱柳(Cylocarya Iljinskaya)为核桃科(Juglandaceae)植物，为中国中南部特有的单一存活种。从古新世到上新世，该属有丰富的北美和欧亚化石记录，记录了它在渐新世期间从欧洲蔓延到西西伯利亚，并在中新世到达日本。然而，在其现代分布附近还没有发现青钱柳的化石。本文描述了云南西部中国梁河县上中新统南林组中的一新种，并对其生物地理意义进行了讨论。方法论。利用光镜和扫描电子显微镜对果实进行了观察，并与青钱柳化石和现存青钱柳果实的形态进行了比较。关键成果。青钱柳的化石果实。11月由一个被圆形凸缘状翅膀包围的小坚果组成。螺母在平面上是圆形的，在纵向上是扁平的。坚果的结构和翅的表皮特征表明，该化石果实与现存的物种青冈几乎完全相同。结论。本文报道的标本是中国发现的唯一可靠的青钱柳化石。这一新化石种有助于填补青钱柳化石记录中的一个重大空白，表明该属在中新世晚期已达到其现代分布的最西边界。滇西晚第三纪气候温暖湿润，上新世云南高原开始快速隆升。更新世冰川可能迫使青钱柳从云南西部撤退，而隆起的山脉和深深的河谷可能为间冰期期间的重新连接设置了障碍。
Premise of research. Cyclocarya Iljinskaya (Juglandaceae) is a genus with a single living species that is endemic to central and south China. The genus has an abundant North American and Eurasian fossil record from the Paleocene to the Pliocene, documenting its spread across Europe to western Siberia during the Oligocene and its arrival in Japan by the Miocene. However, there have been no fossil occurrences of Cyclocarya near its modern distribution. In this study, we describe a new species of Cyclocarya from the upper Miocene Nanlin Formation in Lianghe County, western Yunnan Province, southwest China, and discuss its biogeographic implications. Methodology. We examined the fossil fruit using LM and SEM, and we compared its morphology with fruits of fossil Cyclocarya and extant Cyclocarya paliurus (Batalin) Iljinsk. Pivotal results. The fossil fruit of Cyclocarya simipaliurus sp. nov. consists of a small nutlet that is surrounded by a circular and flange-like wing. The nutlet is circular in plan view and oblate in longitudinal view. Nutlet structure and the epidermal characteristics of the wing indicate that this fossil fruit is almost identical to that of the extant species, C. paliurus. Conclusions. The specimen reported here is the only reliable fossil of Cyclocarya known from China. The new fossil species helps to fill a significant gap in the fossil record of Cyclocarya, indicating that the genus had reached the westernmost boundary of its modern distribution by the late Miocene. Western Yunnan had a warm and humid climate during the late Neogene, and the rapid uplift of the Yunnan Plateau began in the Pliocene. Pleistocene glaciations may have forced Cyclocarya to retreat from western Yunnan, and the uplifted mountains and deep river valleys might have posed barriers for reconnection during the interglacials.